Abstract
In the Asahi River, heavy rainfall from 12th typhoon(2011) had caused the river channel blockade by sediment discharge due to slope failure and debris flow. These phenomena make large amount of sediment flow into the river shortly, and it changes the river channel characteristics, such as channel shape, aggradation, and grain size distribution. So, it is important to evaluate the sediment transport in river basin scale. In this study, first, we clarified the points of slope failure and the characteristic change in river channel by large-scale sediment discharge using observed data and air photographs. In order to estimate the quantity of sediment discharge, numerical analysis of flood flow, slope failure and debris flow was made. Furthermore, we evaluated sediment budget in the Asahi River basin, and suggested the effectiveness of sediment bypass tunnel.
